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Transferfunction initialisation

#5152  Permalink Top

Transferfunction initialisation

Oct-22-14 08:54:50

Hello,

I want to create a transferfunction in which I initialise the coefficients a,b with an external function call. I do this with:

extends Modelica.Blocks.Continuous.TransferFunction((a,b) =getA(m=26.0))

However, this gives me the error message "missing token ')'". The function getA is rather trivial a:

function getA
  input Real m;
  output Real a[2];
  output Real b[2];
algorithm
  a := {4, 2 * m};
  b := {9, 10};
end getA;

If I try it with one output, it works fine, but I would like to initialise both with one function. Does anyone know how this can be approached?

----------
addition: The goal of this whole exercise is to initialise the transfer function based on some other parameters. With these first parameters, I do some calculations, and this results in the coefficients of the transferfunction. Any other way of implementing this, is perfectly fine with me, of course
----------

Thanks for any pointer.
Bas

Edited by: bjdekruif - Oct-22-14 11:35:43
#5154  Permalink Top

Re: Transferfunction initialisation

Oct-23-14 05:25:24

Hello,

I got it working, and just wanted to post the result if anybody want do the same in the future. If somebody knows a better solution, please feel free to comment on the solution. Anyway:

model PD
   extends Modelica.Blocks.Continuous.TransferFunction(a = p, b = q);
    parameter Real[2] p(start = {1, 1},fixed = false);
    parameter Real[2] q(start = {1, 1},fixed = false);
  initial equation
    (p, q) = getA(m=10.3);
end PD;

With the function getA I can calculate the num and den for a PD controller based on the mass, bandwidth and phase margin.  These are passed to the transferfunction and it simulates now with these coefficients.


Bas

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